The present invention relates to a television receiver provided with a liquid crystal cell as a video display device.
In the television receiver, sound and picture carrier waves pass through an antenna, inducing currents. The carrier currents are converted to intermediate-frequencies and amplified by intermediate-frequency amplifiers. The intermediate-frequency signals are detected to provide an audio signal and a video signal. The video signal is fed to a liquid crystal panel driving circuit for display of a video image. The liquid crystal panel driving circuit composes liquid crystal driving waveforms from the video signal for driving the liquid crystal cell to develop half-tone images. The liquid crystal driving waveforms comprises pulses. However, a frequency band of the pulse signals is very wide to cover a range between zero Hz and several hundred MHz. Accordingly, rapid electromagnetic change by the pulse signals causes the radiation of electromagnetic waves, that is, pulse noises. The pulse noises radiated from the liquid crystal panel and panel driving circuit enter into the antenna, intermediate-frequency amplifier, video signal circuit, and audio signal circuit, causing picture quality and sound quality of the television receiver to remarkably deteriorate.
In order to prevent entering of pulse noises, the circuit of the television receiver is divided into a receiving circuit block and a liquid crystal panel driving circuit block, and both circuit blocks are shielded by surrounding the blocks by metal films, respectively. However, since the surface of the liquid crystal cell can not be shielded, pulse noises radiate from the surface. Accordingly, if the pulse noises from the liquid crystal cell enter into the antenna, the operation of the receiver circuit is greatly disturbed. Such a disturbance is liable to occur in a compact liquid crystal television receiver in which the antenna is closely disposed to the liquid crystal cell.